1. Field of the Invention
The present invention relates to an apparatus for selecting a mattress hardness suitable for the physical constitution of the user such as the body weight and the height.
2. Description of the Related Art
In general, a bed consists of a bed frame and a mattress mounted in the bed frame. To obtain a comfortable sleeping condition it is very important for the mattress to have a hardness suitable for the physical constitution of the user such as the body weight and the height. When the user sleeps lying on the mattress with the face upward, it is generally said that a comfortable sleeping can be obtained in the case where the height of the waist portion based on a plane including both the back portion and the hip portion is about half the corresponding height in the standing state. In other wards, if the bending of the spinal column in the sleeping state is moderate, compared with the bending in the standing state, it is possible to ensure a natural sleeping posture in which an unnatural force is not applied to the internal organs.
In the case of using an unduly soft mattress, the back portion and the hip portion of the user lying on the mattress drop unduly deep into the mattress, resulting in a relative projection of the waist portion. In this case, the height noted above becomes considerably greater than that in the standing state. Of course, the bending of the spinal column of the user also becomes greater, with the result that an unnatural force is applied to the internal organs of the user. It follows that the user feels a pain, failing to sleep comfortably.
Generally speaking, it is desirable to use a hard mattress because the dropping of the back portion and the hip portion can be suppressed. If the mattress is unduly hard, however, the body of the user is supported by some parts of the back portion and the hip portion. In this case, the pressure is concentrated on the back portion and the hip portion, resulting in failure to ensure a comfortable sleeping.
Suppose a mattress is selected in view of the hardness thereof alone. In this case, the actual dropping amount of the back portion and the hip portion of the user depends on the physical constitution of the user such as the body weight and the height. It follows that, in selecting a mattress, it is also important to consider the physical constitution of the user such as the body weight and the height in addition to the hardness of the mattress. In other words, it is important to select a mattress suitable for the physical constitution of the user.
Japanese Patent Application No. 61-25329 (corresponding to Japanese Patent Disclosure (KOKAI) No. 62-183715), discloses an apparatus for selecting a mattress suitable for the user. This prior art teaches that, when a user lies on a measuring mattress, arm-like displacement members are swung in accordance with the elastic deformation of the measuring mattress. An interlocking rod, which is connected to each displacement member, is interlocked with the swinging of the displacement member so as to slide in a vertical direction. The upper ends of the interlocking rods are connected to each other by a single string. It follows that the string depicts a graph showing the state of deformation of the measuring mattress on which the user lies.
The deformation state of the measuring mattress depicted by the string permits the user to determine whether the measuring mattress is hard or soft to the user, making it possible for the user to select a mattress of a hardness suitable for the user himself.
In the prior art cited above, however, the elastic deformation of the measuring mattress is mechanically transmitted by the body of displacement and the interlocking rods, resulting in an increase in the number of parts used and in a complex structure of the system. In addition, the parts of the apparatus can be damaged in an early stage of use by abrasion, leading to an erroneous transmission of the elastic deformation of the measuring mattress.